bufferWithTime restart buffering after window is closed
bufferWithTime window opening signaling corrected.
bufferWithTime and buffer corrected, tests created
Merge branch 'master' of https://github.com/github/ReactiveCocoa

Conflicts:
	ReactiveCocoaFramework/ReactiveCocoaTests/RACSignalSpec.m
Corrections based on  previous comments by @joshaber. Changed tests to include NSNull conversion testing.
Merge branch 'master' of https://github.com/github/ReactiveCocoa
Style errors corrected.
Style changes.
Merge pull request #206 from andrask/master

bufferWithTime restarts buffering when window closed